|Publication number||US8138042 B2|
|Application number||US 12/967,238|
|Publication date||Mar 20, 2012|
|Filing date||Dec 14, 2010|
|Priority date||Mar 29, 2007|
|Also published as||US7859081, US20080237675, US20110079837|
|Publication number||12967238, 967238, US 8138042 B2, US 8138042B2, US-B2-8138042, US8138042 B2, US8138042B2|
|Inventors||Brian S. Doyle, Robert S. Chau, Suman Datta, Vivek De, Ali Keshavarzi, Dinesh Somasekhar|
|Original Assignee||Intel Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (48), Referenced by (2), Classifications (16), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a divisional of U.S. patent application Ser. No. 11/731,543, now U.S. Pat. No. 7,859,081, which was filed on Mar. 29, 2007.
The disclosed embodiments of the invention relate generally to capacitors, and relate more particularly to fin capacitors capable of use in embedded memory applications.
Today's computer chips are increasingly dependent on robust memory architecture capable of quickly accessing and handling large amounts of data. Existing memory solutions such as off-chip physical dynamic random access memory (DRAM) that sit on the mother board separate from the computer chip require relatively large amounts of energy and suffer from high latency, resulting in power-performance loss. Latency problems have been addressed using 1T-1C DRAM cells embedded on the computer chip, but existing versions of such DRAM cells are frequently unable to meet ever-increasing capacitance demands. Accordingly, there exists a need for a large-size, high-density capacitor compatible with a 1T-1C embedded DRAM cell usable within a logic technology process.
The disclosed embodiments will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying figures in the drawings in which:
For simplicity and clarity of illustration, the drawing figures illustrate the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the discussion of the described embodiments of the invention. Additionally, elements in the drawing figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present invention. The same reference numerals in different figures denote the same elements.
The terms “first,” “second,” “third,” “fourth,” and the like in the description and in the claims, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Similarly, if a method is described herein as comprising a series of steps, the order of such steps as presented herein is not necessarily the only order in which such steps may be performed, and certain of the stated steps may possibly be omitted and/or certain other steps not described herein may possibly be added to the method. Furthermore, the terms “comprise,” “include,” “have,” and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “over,” “under,” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein. The term “coupled,” as used herein, is defined as directly or indirectly connected in an electrical or non-electrical manner. Objects described herein as being “adjacent to” each other may be in physical contact with each other, in close proximity to each other, or in the same general region or area as each other, as appropriate for the context in which the phrase is used.
In one embodiment of the invention, a capacitor comprises a substrate, a first electrically insulating layer over the substrate, and a fin comprising a semiconducting material over the first electrically insulating layer. A first electrically conducting layer is located over the first electrically insulating layer and adjacent to the fin. A second electrically insulating layer is located adjacent to the first electrically conducting layer, and a second electrically conducting layer is located adjacent to the second electrically insulating layer. The first and second electrically conducting layers together with the second electrically insulating layer form a metal-insulator-metal stack that greatly increases the capacitance area of the capacitor.
Referring now to the figures,
Capacitor 100 further comprises an electrically conducting layer 140 over electrically insulating layer 120 and adjacent to fin 130, an electrically insulating layer 150 adjacent to electrically conducting layer 140, and an electrically conducting layer 160 adjacent to electrically insulating layer 150. An inter-layer dielectric (ILD) 170 is over electrically insulating layer 120 and at least partially surrounds fin 130. In a non-illustrated embodiment, capacitor 100 may be a decoupling capacitor. In the illustrated embodiment, capacitor 100 comprises a tri-gate storage capacitor, with the three gates located at the three interfaces between a face of fin 130 and an adjacent portion of electrically conducting layer 140, that may be used along with a tri-gate transistor as part of a 1T-1C DRAM cell. Such an arrangement will be further discussed below.
In one embodiment, electrically insulating layer 150 comprises a high-k dielectric material such as hafnium oxide (HfO2), zirconium oxide (ZrO2), lanthanum oxide (LnO2), or the like, including combinations and/or laminates thereof, each of which have dielectric constants of approximately 20 to approximately 40. Compare this to silicon dioxide which was for many years widely used as a gate dielectric material and which has a dielectric constant (κ) of approximately 3.9. (Although the dielectric constant is often represented by the Greek letter κ, it is usually the lower case Roman letter “k” that is used in such phrases as “high-k dielectric material,” and that convention will be followed here.) The dielectric constant of a vacuum, which is used as a scale reference point, is defined as 1. Accordingly, any material having a dielectric constant greater than about 5 or 10 would likely properly be considered a high-k material.
Existing DRAM capacitors based on tall fin architecture are characterized by a small capacitance area relative to the bitline capacitance that it needs to influence, and therefore require dielectrics with very high dielectric constants—perhaps much higher than the values around 20 to 40 that were mentioned in the preceding paragraph. Such dielectrics do exist, as for example lead zirconium titanate (PZT), which may have a dielectric constant greater than 100 and possibly approaching 500 or higher. Such materials, however, are often not compatible with wafer processing techniques and temperatures. Furthermore, materials with higher dielectric constants tend to leak charge more than those with lower dielectric constants, requiring more frequent rewriting or refreshing of the charge. Accordingly, although high-k dielectric materials may enhance capacitor performance, such materials must be carefully chosen in order to avoid problems such as those mentioned in this paragraph.
In at least one embodiment of the present invention, a capacitor's capacitance area is increased so that the capacitor is able to properly influence its bitline capacitance using a material having a dielectric constant large enough that it may properly be considered a high-k material but not so large that it is likely to lead to processing or charge refresh problems. As an example, capacitor 100 has an increased capacitance area that follows a linear distance marked by a length of electrically insulating layer 150. Such a capacitance area is greatly enhanced over that of a capacitor in which the metal-insulator-metal (MIM) stack is confined to the immediate region around fin 130, or to a similarly modest area.
Referring still to
In one embodiment, electrically insulating layer 120 comprises an electrically insulating material, and in the same or another embodiment, electrically conducting layer 140 comprises an electrically conducting material. (In another embodiment electrically conducting layer 140 can comprise a semiconducting material.) In one embodiment, as mentioned above, the electrically insulating material of electrically insulating layer 120 is an oxide material. In the same or another embodiment, the electrically conducting material of electrically conducting layer 140 can be a metal having a work function that lies approximately mid-way between a conductive band and a valence band of the oxide or other electrically insulating material of electrically insulating layer 120. A material having a work function as described may be used to control leakage. As an example, the metal can be titanium nitride (TiN), tantalum nitride (TaN), or the like.
In one embodiment, electrically conducting layer 160 comprises an electrically conducting material that is the same as the electrically conducting material making up electrically conducting layer 140. In a different embodiment, however, electrically conducting layer 160 comprises an electrically conducting material that is different from the electrically conducting material making up electrically conducting layer 140. Using different electrically conducting materials may be desirable when, to take one example, processing issues dictate that one of the electrically conducting materials be more etchable than the other electrically conducting material.
A step 310 of method 300 is to deposit an inter-layer dielectric having an inter-layer dielectric surface over the first electrically insulating layer and around the tri-gate capacitor and the tri-gate transistor. As an example, the inter-layer dielectric can be similar to inter-layer dielectric 270, shown in
A step 320 of method 300 is to form a trench in the inter-layer dielectric in which at least a portion of the first semiconducting fin is exposed. The processing steps that form the trench may differ from one embodiment to another, and such processing differences may depend at least in part on the material that is adjacent to the exposed portion of the semiconducting fin. In the embodiment illustrated in
As an example, the exposed surface of the electrically conducting material can be similar to a surface 410, first shown in
Referring still to
A step 330 of method 300 is to conformally deposit a first metal layer over the inter-layer dielectric surface and the electrically insulating film, in the trench, and over the first semiconducting fin. The first metal layer comprises a first metal that makes ohmic contact with the semiconducting fin, and that acts as the bottom electrode of the tri-gate capacitor. As an example, the first metal layer can be similar to electrically conducting layer 140, shown in
A step 340 of method 300 is to conformally deposit a second electrically insulating layer over the first metal layer. As an example, the second electrically insulating layer can be similar to electrically insulating layer 150, shown in
A step 350 of method 300 is to conformally deposit a second metal layer over the second electrically insulating layer. The second metal layer comprises a second metal that acts as the top electrode of the tri-gate capacitor. In one embodiment, the second metal layer fills or substantially fills the trench. As an example, the second metal layer can be similar to electrically conducting layer 160, shown in
A step 360 of method 300 is to remove portions of one or more of the first metal layer, the second electrically insulating layer, the second metal layer, and the electrically insulating film. As an example, step 360 places tri-gate memory cell 200 in a condition such as that illustrated in
In one embodiment, step 360 comprises creating an upper extremity of the second electrically insulating layer, and method 300 further comprises recessing the second metal layer below the upper extremity of the second electrically insulating layer. As an example, the upper extremity of the second electrically insulating layer can be similar to a surface 1111, first shown in
A step 370 of method 300 is to adjust a height of the first semiconducting fin. Step 370 is an optional step that may in some embodiments not be performed. In an embodiment where step 370 is performed, a surface of the first electrically insulating layer is a first surface, the semiconducting fin has a second surface, the second electrically conducting layer has a third surface, a width of the trench is a first distance, a distance between the first surface and the second surface is a second distance, and a distance between the second surface and the third surface is a third distance. As an example, the first surface, the second surface, and the third surface can be similar to, respectively, surface 121, surface 137, and surface 161, all of which are shown in
In an embodiment that is an alternative to the embodiment that has just been described, the ILD fills the region that in the foregoing embodiment was occupied by polysilicon, and in this alternative embodiment polysilicon is only present around the tri-gate transistor and not around the tri-gate capacitor. In this alternate embodiment the wet etch to remove polysilicon is not needed and is replaced by a dry etch of the oxide or other material making up the ILD. The other steps of method 300 may be used in this alternate embodiment without change from the way they are set forth in the previously-described embodiment. A possible advantage of the embodiment just described is that compared to other embodiments described herein it results in a greater amount of lateral space (equivalent to dimension 145 in
Capacitor 1200 may be constructed in the same manner as that described above for capacitor 100 by making appropriate adjustments to the placement of the resist layer as readily understand by one of ordinary skill in the art. The construction of capacitor 1200 may be easier than that for capacitor 100 because the layout of capacitor 1200 provides more margin for the metal fills. Both capacitors 100 and 1200 require that five layers be fit into their respective trenches. Yet for equal trench widths (the trench widths are represented by distance 145 (see
As an example, electrically insulating layer 1220 can be an oxide slab having a surface 1221. As another example, semiconducting material 1235 can be silicon (Si), germanium (Ge), silicon germanium (SiGe), a III-V material such as gallium arsenide (GaAs), or the like. As yet another example, fin 1230 can extend at least part way into electrically insulating layer 1220. In one embodiment, for example, fin 1230 has a portion 1231 extending into electrically insulating layer 1220 and a portion 1232 protruding from surface 1221 of electrically insulating layer 1220. In the illustrated embodiment, portion 1231 extends all the way through electrically insulating layer 1220 and into substrate 1210. In the same or another embodiment, fin 1230 can be degenerately doped down to or below surface 1221, and/or can be made electrically conducting through silicidation or the like.
Capacitor 1200 further comprises an electrically conducting layer 1240 over electrically insulating layer 1220 and adjacent to fin 1230, an electrically insulating layer 1250 adjacent to electrically conducting layer 1240, and an electrically conducting layer 1260 adjacent to electrically insulating layer 1250. An ILD 1270 is over electrically insulating layer 1220 and at least partially surrounds fin 1230. In a non-illustrated embodiment, capacitor 1200 may be a decoupling capacitor. As was also the case for capacitor 100, capacitor 1200 may be used along with a tri-gate transistor as part of a 1T-1C DRAM cell. Such an arrangement was discussed in more detail above. However, like
In one embodiment, capacitor 1331 comprises a tri-gate storage capacitor and memory device 1330 further comprises a transistor 1332 adjacent to capacitor 1331. Transistor 1332 can be similar to tri-gate transistor 240, first shown in
Although the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes may be made without departing from the spirit or scope of the invention. Accordingly, the disclosure of embodiments of the invention is intended to be illustrative of the scope of the invention and is not intended to be limiting. It is intended that the scope of the invention shall be limited only to the extent required by the appended claims. For example, to one of ordinary skill in the art, it will be readily apparent that the capacitor and related methods and systems discussed herein may be implemented in a variety of embodiments, and that the foregoing discussion of certain of these embodiments does not necessarily represent a complete description of all possible embodiments.
Additionally, benefits, other advantages, and solutions to problems have been described with regard to specific embodiments. The benefits, advantages, solutions to problems, and any element or elements that may cause any benefit, advantage, or solution to occur or become more pronounced, however, are not to be construed as critical, required, or essential features or elements of any or all of the claims.
Moreover, embodiments and limitations disclosed herein are not dedicated to the public under the doctrine of dedication if the embodiments and/or limitations: (1) are not expressly claimed in the claims; and (2) are or are potentially equivalents of express elements and/or limitations in the claims under the doctrine of equivalents.
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|U.S. Classification||438/253, 257/E21.014, 438/254, 438/584, 438/238, 438/585, 438/284, 438/396, 438/381, 438/239|
|Cooperative Classification||H01L27/10852, H01L28/91, H01L29/785|
|European Classification||H01L27/108M4B2, H01L28/91|